Displays, LED illuminations, light condensations, information transmissions and the like all need optical curved surfaces to improve system performance and reduce system energy consumption. Conventional optical curved surfaces are mainly machined by using expensive multi-axis computerized numerical control (CNC) precision machine tools. The machining needs many processes such as rough grinding, fine grinding, polishing and the like. Therefore, wear of the tools is severe, the CNC machine tools are difficult to control, and the processing efficiency is extremely low. In addition, a large quantity of emissions which are difficult to recycle is produced, while the cost is high, the efficiency is low and the cutting liquid is not environmentally friendly.
Therefore, micro-cracks are formed under induction of precise and smooth micro-grinding tips, and an optical curved surface is formed by controlling micro-crack expansion and brittle fracture forming, which is fast, low in cost and good in effect. In addition, a relevant mechanical model is established, which may be used to predict the force suffered during processing.
At present, cemented carbide and PCD cutter wheels are widely used to split glass, but the cutter has a limited life time. Therefore, a harder CVD diamond wheel is invented to replace the cemented carbide and PCD cutter wheel. However, cutting the glass with a cutter wheel inevitably causes damages to edges and unevenness of the cross section. Cutting glass using an ultrasonic vibration assisted diamond cutter wheel for scribing could increase the longitudinal depth of the micro-crack and is thus favorable to cutting of the glass. However, the damages on the edges and unevenness of the cross section are still not solved, and further grinding is still needed.
Although scribing using the diamond plus irradiating along the microgroove using laser is favorable cutting of the glass, the damages on the edges are still not addressed, and additionally an oblique cross section is produced. Scribing the glass using laser irradiation and irradiating micro-marks may achieve the purpose of splitting the glass. However, edge damages and burrs are unavoidable, and thermal damages are present in the cross section. As such, the cross section still needs further treatments.
Laser and chemical corrosion may be used for machining of the micro-tips of the hard and brittle materials. However, the machining depth is less than 7.5 μm and the surface of the microgroove is irregular and rough. The micro-tip of the diamond wheel is used to machine micro-grooves which are precise and smooth.
Precise and smooth micro-grinding tip-induced cutting of the optical materials requires no additional procedures, and may complete precise and mirror machining at one time.